Prior art for wind turbines most commonly seen in photographs and video, and having a horizontal axis, suffers from several problems. Foremost is that it is not very efficient in terms of C-sub-p or maximum power coefficient unless made in large scale, suitable only for some geographical areas. These devices also require auxiliary equipment to align the rotating axis constantly with the current wind direction, and separately to start the rotation when wind resumes after a period of nil or small wind.
Vertical axis wind turbines have been taught and have the advantage of not requiring external alignment and start-up equipment, but they have been relatively inefficient. There has been a need for an efficient vertical axis wind turbine that can be erected with small dimensions, suitable for suburban or possibly even urban installation while producing enough electric power to be economically worthwhile to install.
The vertical wind turbine of VanDerHye et al., U.S. Pat. No. 7,314,346, differs from the one disclosed here in two respects, although both are based on the well-known Savonius design first disclosed in U.S. Pat. No. 1,697,574. First, the VanDerHye device requires careful manufacture of the blades to a precise mathematical formula, which is an economic drawback. Second, the VanDerHye device has blades that are not enclosed top and bottom and thus allow air (or other driving fluid) to spill out of the blades and reduce efficiency. The device disclosed here uses an enclosed design (top and bottom of each blade set or rotor) to prevent that.
Like the Benesh design, first disclosed in U.S. Pat. No. 5,494,407, the blades in the current invention are fixed to upper and lower plates. However, unlike 407, here there are no linear (in cross section) or flat portions of the blades, or any overlap where a blade is parallel to another blade. Moreover, here the turbine consists of not one but three or more blade-sets, angularly offset from one another.
The enclosed vertical axis fluid rotor acting as a wind turbine disclosed here is self-starting, needs minimal alignment, and operates efficiently at a wide range of wind or water current speeds (producing more electric power at higher speeds). It produces substantial power in relatively small size scales, but can be scaled up readily. It is suitable for operation in both air current (wind) and water current.